Thermostatic switch



A118- 30, 1949- R. aowLAND THERMOSTATIC SWITCH Filed May :51, 1946 jaw@ mf Mw? s cxaw,

Patented Aug. 30, 1949 UNITED sTATEs PATENT OFFICE 2.480,216 A THERMOSTATIC SWITCH Richard Bowland, Spring Valley, Ill., assignor to Sampsel Time Control, Inc., Spring Valley, Ill., a corporation of Illinois Application May 31, 1946, Serial No. 673,264 4 Claims. (Cl. 20G-139) My invention relates to adjustable thermostats primarily adaptable for use in a heating system of the general type described in Miller Patent No. 2,132,513, dated October 11, 1938.

More specifically, my invention relates to an improvementI in a switch which is actuated by the temperature of a. room to control through a suitable relay an electrical circuit which is designed .primarily to actuate fuel feeding and associated apparatus for a house heating system.

A particular object of my invention is to provide a thermostatic device of the character mentioned which is sensitive and accurate, which is manually adjustable to maintain within selected limits a predetermined room temperature, and

proceeds. I Referring now to the drawing, forming a part of this specification and illustrating a preferred embodiment of my invention- Fig. 1 is a. plan view of a thermostatic switch embodying my invention; and

Fig. 2 is a side elevational view of the same.

The numeral I illustrates a base plate form'ed preferably of plastic or other suitable insulating material. Formed integrally with the base plate Ill is a horseshoe-shaped socket I2 in which is secured, as by means of a screw I3, a permanent magnet I4, a semi-circular clamping washer I6 being provided between the screw head and the magnet.

Also formed integrally with the base plate Ill is a mounting block or lug I8 to which is secured a switch actuating device indicated generally by the numeral 20. Said device comprises a U-shaped bimetallic blade 2| which is preferably slotted as at 22. A spring metal extension 26 attached to the bimetal 2| is clamped as by screws or rivets 26 to the lug I8 and carried by the bimetal is an arm 26 having an angular linger 26 on the end thereof, which bears against a circular cam 30. The cam 30 is carried by a disc 32 which is rotatably mounted on the base plate and aiiixed-to said disc, as by screws 33, is an indicia plate 36. As seen best in Fig. 1, the plate 36 carries temperature indicia. The screws 33 pass through slots Sein the indicia plate whereby 2 said plate may be adjusted relative to the disc 32 for calibration of the device.

The bimetallic blade 2| is secured, as by screws 40, to a. U-shaped spring steel connecting member 42 which carries as an extension a contact plate 42, the free end portion of which extends over the permanent magnet I4. A Calibrating screw 45 is threaded through one leg of the U-member 42, in this case the lower leg thereof, while it tunis freely in the other leg thereof, so that by rotating the screw 45 the legs of the member 42 are brought closer together or farther apart; thus the distance of the contact member 42 from the face of the magnet I4 is varied without appreciably varying the area of overhang.

Secured to the base plate l0, as by means of a screw 41, is an angular contact bracket 50, one arm 5I of which extends over the contact plate 42, a contact head 53 being provided on the end of a screw 54 threaded through the arm 5I. Axially aligned with the screw 54 is a contact member 58 carried by a. screw 51 on which is arranged a. pointer 59. A segmental indicia plate 60 is secured to the base plate under the pointer 59. Contact buttons 6| are secured to the plate 42.

Suitable conductors (not shown) extend from the contact plate 50, from the indicia plate 60, the latter being electrically connected to the member 5l, and from contact plate 62, electrically connected to member 26.

The operation of the switch-described above ,will be clear to those skilled in the art. .The

switch operates in a well known way as a snap action thermostatic switch by reason of the effect of the permanent magnet I4. When the bime-v tallic blade 2| is cold the contact plate 42 will be in engagement with the element 56 and current will accordingly flow from bracket 62 and blade 2| through the member 51 and bracket 60 on through a suitable conductor to a relay, etc. for performing certain functions in a heating system (such last mentioned parts not being shown inasmuch as they are standard in this art).

When the bimetallic blade has warmedup to a degree determined by adjustment of the cam 30 and the pointer 59, the contact plate 42 will be snapped, in opposition to the inuence of the magnet, into engagement with the contact head 63 and then current will flow from the blade 2| through the contact bracket 50 and on through a conductor to a relay, etc., for performing other functions in the heating system (the latter elements again not being shown).

Adjustment of the pointer 59 through the arc indicated on the scale 60 raises and lowers the aecomo 3 contact head 56 so as to increase or reduce the period between movements of the contact plate 42, in a manner well known in the art.

It will be seen that adjustment of the contact plate 42 by means of the adJusting screw 45 serves only to move said plate in a direction perpendicular to the face of the magnet i5, toward or away from said magnet, there being no appreciable motion in any other direction. Hence, the pull of the magnet on said plate 42 will always be substantially the same by reason of the constant overlapping area of the plate relative to the mag net, and hence calibration of the device may be more rapid and accurate than would otherwise be possible.

Various changes coming within the spirit ofy my invention may suggest themselves to those skilled in the art, and hence I do not .wish to be limited to the specific form shown or uses mentioned except to the extent indicated in the appended claims, which are to be interpreted as broadly as the state of the art will permit.

I claim:

1. In a temperature responsive electrical switch, a base member, a permanent magnet, a bimetallic U-shaped blade, the short leg of said blade being fixedly secured to said base, cam adjusting means operating on said leg. a U-shaped least one of said switch contacts is adjustable toward and away from the other.

4. A switch as deined in claim 1 wherein at least one of said switch contacts is adjustable toward and away from the other.

RICHARD BOWLAND.

REFERENCES CITED I The following references are of record in the le of this patent:

UNITED STATES PATENTS Date Number Name 1,290,928 Denison Jan. 14, 1919 2,145,722 Hall -..s Jan. 31, 1939 2,249,259 Shaw July 15, 1941 2,250,135 Lindemann July 22, 1941 2,263,988 Hardy et al. Nov. 25, 1941- 

